Bamboo Airways signed a provisional deal to buy 20 Boeing 787-9 wide-body jets worth $5.6 billion at list prices in July, as well as a memorandum of understanding with Airbus for up to 24 A320neo narrow-bodies in March.

Last week, Vietjet signed a $6.5 billion agreement to buy 50 Airbus A321neo jets, part of aggressive investment in the airline's fleet, which has provided lucrative business for both European aerospace group Airbus and U.S. rival Boeing.